The present invention relates to disposable absorbent articles, such as incontinence garments for infants, children, and adults, including disposable underwear, disposable diapers, disposable pull-on diapers, disposable training pants, and disposable panties for menstrual use. More specifically, the present invention relates to disposable absorbent articles that include retention zones for preventing slippage of the absorbent article relative to the body of a wearer during the time the article is worn.
Infants and others who are incontinent wear disposable absorbent articles such as diapers or other absorbent undergarments to receive and contain urine and other bodily exudates. Absorbent articles in the form of garments that are pre-assembled for slip-on application on the body of a wearer (e.g., training pants or pull-on diapers) have recently become popular. In order both to contain bodily exudates and also to fit a wide variety of body shapes and sizes, such garments must fit snugly about the waist and legs of the wearer without drooping, sagging, or sliding down from their position on the lower torso, and without causing unnecessary pressure on the skin by reason of the product being too tight for the wearer""s comfort.
Many types of pull-on garments use conventional elastic elements secured in an elastically contractible condition in the waist and leg openings. For example, pull-on absorbent garments known as xe2x80x9cballoon typexe2x80x9d pants include elasticized bands in specific zones of the product that are in contracted form, while the remaining material tends to blouse. Examples of such pull-on garments are disclosed in U.S. Pat. No. 5,171,239 published on Dec. 15, 1992, U.S. Pat. No. 4,610,681 published on Sep. 9, 1986. Those garments will fit a range of waist and leg sizes because the elastic portions will expand to accommodate various size wearers. Nonetheless, the range of sizes is limited because the elastic elements, which enable this variation in size, have a limited degree of stretch. The narrow elastic bands used in the waist opening and the leg openings also tend to concentrate the fit forces in a narrow zone of the wearer""s body leading to increased incidence of skin marking of the wearer.
Other types of pull-on, absorbent garments that employ waist elastics and side elastics are disclosed in U.S. Pat. No. 4,940,464, published on Jul. 10, 1990, U.S. Pat. No. 5,246,433, published on Sep. 21, 1993, U.S. Pat. No. 5,591,155, published on Jan. 7, 1997, EP publication 0 526 868 A1 published on Feb. 10, 1993, U.S. Pat. No. 5,545,158 published on Aug. 13, 1996; and EP publication 0 547 497 A2, published on Jun. 23, 1993.
Disposable, absorbent garments of the type identified above are generally held in position on the body of the wearer by an elasticized structure that is positioned in the waist area of the garment. The elasticized structure is preferably under tension to generate a hoop stress within the waist structure and cause it to engage with and to press against the waist area of the wearer. And to minimize downward slippage or drooping of such garments while they are worm, the hoop stress within the elasticized waist structure must be large enough to cause an inward force of sufficient magnitude to press against the skin at the wearer""s waist. The inward force should be great enough to provide a normal force against the wearer""s body to result in sufficient friction between the wearer""s skin and the inner surface of the elastic waist structure to overcome those forces that act to tend to pull the garment down from the wearer""s waist, away from garment""s initial position when it was first applied to the wearer. In that regard, the downward forces acting on the garment to pull it down are caused, in part, by movements by the wearer, and they are also caused, in part, by an increase in the weight of the absorbent, exudate-receiving core, which results from the absorption and containment by the absorbent core of waste products in the form of urine and fecal material.
But in providing sufficient hoop stress within the elasticized waist structure to attempt to cause the garment to be retained in its initial position on the wearer""s body, the inward force acting against the wearer""s waist causes pressure and tightness to be exerted on the body of the wearer, which can cause wearer discomfort, and can also cause undesirable pressure marks, sometimes referred to as xe2x80x9cred marks,xe2x80x9d on the wearer""s skin about the wearer""s waist. Such red marks are indicative of the relatively high inward forces that are imposed on the wearers waist, and they are undesirable both because they cause discomfort to the wearer and also because they cause anxiety to mothers of small children who wear such garments. The present invention is directed to minimizing such discomfort and the attendant red marking of the wearer""s skin by providing increased surface static friction between the garment and the wearer""s skin, which enables the hoop stress, and the resulting inward forces acting against the wearer""s body, to be reduced. Additionally, because it enables lower pressure forces against the skin of a wearer, the present invention also serves to reduce skin abrasion resulting from relative movement of portions of such garments and the wearer""s skin.
The broad notion of increasing the coefficient of friction of an interior surface of a disposable diaper is disclosed in U.S. Pat. No. No. 5,782,819, entitled xe2x80x9cArticle with Stay-In-Place Feature,xe2x80x9d which issued on Jul. 21, 1998, to Tanzer et al., and in Intemational Patent Publication No. WO 95/22306, entitled xe2x80x9cAbsorbent Pant Diaper,xe2x80x9d which was published on Aug. 24, 1995, in the name of Kling et al. as inventors. However, the latter does not disclose particular values of coefficient of friction, and it teaches placement of a friction agent at the hip portions of the diaper, but not over the side seams and not in the back portions of the diaper. And the former discloses an arrangement wherein the dynamic coefficient of friction has a first value when movement occurs in a first direction, and a second value when movement occurs in the opposite direction.
It is an object of the present invention to provide a disposable absorbent article that includes a relatively high coefficient of static friction at selected portions of the skin-facing surfaces of the article, to retain the article in its desired wearing position during movements by the wearer.
It is another object of the present invention to provide a disposable absorbent article that includes a relatively low coefficient of static friction on selected portions of the structure to facilitate application of the article to the body of a wearer and also to facilitate removal therefrom.
Briefly stated, in accordance with one aspect of the present invention, a disposable garment is provided that has a chassis that includes a topsheet, a backsheet joined with the topsheet, and an absorbent core interposed between the topsheet and the backsheet. The chassis has a front region, a back region, a crotch region between the front region and the back region, and side edges and end edges. A pair of side seams join portions of the side edges of the chassis at the front region to other portions of the respective side edges of the chassis at the back region to form a garment having pair of laterally spaced leg openings and a waist opening spaced from each of the leg openings. At least one retention zone is positioned interiorly of the garment at the waist opening and overlying a side seam. The retention zone has a coefficient of static friction that is at least about 200% greater than that of other body-contacting portions of the waistband, to assist in retention of the garment in a desired wearing position on the body of a wearer.
In accordance with another aspect of the present invention, the disposable garment includes slip zones within the interior, body-facing surface of the garment to facilitate application and removal of the garment from the body of a wearer. The slip zones have a relatively low coefficient of static friction, of the order of less than about 0.20. The slip zones can be positioned on the inner surface of the waistband at points between the retention zones, or on the portion of the waistband that overlies the wearer""s stomach when the garment is worn, or they can be positioned around the interior surface adjacent the leg openings to reduce drag during application and removal of the garment. Moreover, zones of intermediate coefficient of static friction, within the range of from about 0.20 to about 1.5, can be positioned between the retention zones and the slip zones.
In accordance with a further aspect of the present invention, the inner surface of the waistband can include one or more pivotable flaps. In one position of the flaps an area of relatively high coefficient of static friction is covered and in a second, pivoted position of the flaps the high coefficient of static friction area is exposed to the skin of the wearer. The flap material that pivots about a pivot axis that is substantially parallel with the circumference of the waistband to expose an area having a coefficient of static friction of the order of from about 0.20 to about 1.5.